Method and composition for suppressing the nitrification of ammonium nitrogen in soil



United States Patent Office 3,01 1,886 Patented Dec. 5,1961

The present invention relates to crop culture and is particularlyconcerned with a new agronomical practice and composition for conservingsoil nitrogen and for supplying the soil nitrogen requirements for plantnutrition.

Since the majority of plants obtain most or all of their nitrogenrequirements from the soil,'the adequate provision of nutrient nitrogenin soil for plant growth is one of the foremost agronomic problems. Thenitrogen in the soil is found to occur primarily in three forms: organicnitrogen, ammonium nitrogen and nitrate nitrogen, of which ammoniumnitrogen and nitrate nitrogen are the primary forms utilized by plants.This nitrogen is absorbed by plants in solution from the soil in theform of ammonium ions and nitrate ions.

The organic nitrogen in the soil consists of a large number of compoundsand originates from manure, crop residues, organic fertilizers orbacterial syntheses. Since with the exception of the organic reducednitrogen fertilizers such as urea, the solubility of these compounds inwater is very low, they are not readily leached from the soil, butneither are they directly available to the plants for use. In order tobe available to the plants, the nitrogen in the organic compounds mustbe converted by soil bacteria to ammonia or inorganic ammonium salts.This conversion, when from organic reduced nitrogen ertilizers such asurea, takes placevery rapidly, but very slowly when from other organicnitrogen compounds. Fol-lowing the, conversion, the ammonium nitrogen isvery rapidly oxidized by soil bacteria to inorganic nitrate nitrogen. Inthis process, the ammonium nitrogen is first oxidized to theintermediate nitrite nitrogen which is then rapidly oxidized to nitratenitrogen. ization of organic nitrogen constantly replenishes thesoilwith nitrogen available for plant absorption.

The ammonium nitrogen in the'soil is derived from bacterial conversionof organic nitrogen or from the added reduced nitrogen fertilizers suchas, anhydrous ammonia, aqueous ammonia, ammonium phosphate, ammoniumnitrate and ammonium sulfate. These ammonium compounds or inorganicreduced nitrogen compounds are readily soluble in water or aqueous soilmedium. When in solution, the reduced nitrogen occurs largely as theammonium ion. Due to the cationic nature of this ion, the ion isstrongly adsorbed on the soil colloids or base exchange complex of thesoil. This colloidal-bound ammonium nitrogen exists in equilibrium witha small concentration of ammonium ions in the soil solution. Thus, thecolloidal-bound ammonium nitrogen provides a dynamic nitrogen reservoirto maintain a supply of ammonium ions in the soil solution for plantadsorption. Further, since the ammonium nitrogen in thesoil occursprincipally as colloidal-bound nitrogen, only very small quantities ofthe ammonium form of soil nitrogen are lost from the feeding zone of theplants by leaching.

' The nitrate nitrogen-in the soil is derived from the.

oxidation or nitrification of ammonium nitrogen by soil bacteria, or bythe addition of inorganic nitrate fertilizers such as ammonium nitrate,sodium nitrate, potassium nitrate and calcium nitrate. The inorganicnitrate compounds are readily soluble in water and the aqueous soil Thismineralmedium. When so dissolved, the nitratenitrogen largely Because ofthe anionic nature exists as the nitrate ion. of this ion, nitratenitrogen is not adsorbed by soil colloids.

Accordingly, the nitrate nitrogen is rapidly leached by rainfall andirrigation and readily lost from the feeding zone of the plants.Further, the nitrate nitrogen is reduced by many soil bacteria tonitrogen gas. process is known as denitrification and account for "anadditional loss of large quantities of nitrate nitrogen from I the soil.The yearly loss from leaching and denitrification amounts to from 20 topercent of the nitrate nitrogen found in the soil, whatever its source.

Nitrification or the conversion of the ammonium nitrogen in soil tonitrate nitrogen by bacterial action occurs at a rate which is dependentprimarily upon the soil temperature and the soil pH. The rate is alsosomewhat dependent upon the type of soil and the moisture content of thesoil. Therate of nitrification is rapid when the soil temperature is atleast 10' C. and the soil pH is at least 5. For example, the conversionof ammonium nitrogen to nitrate nitrogen in sand, silt or clay loam soilhaving a pH of at least 6 may take place at a rate of from 20 pounds ofnitrate nitrogen per acre per week at 10 C., to 500 pounds of nitratenitrogen per Week at 35 C. Even at temperatures as low as 2 C.,nitrification will oftentimes occur in such soils at a rate of 25 poundsof nitrate nitrogen per month. Thus, ammonium nitrogen is very rapidlychanged to nitrate nitrogen in most agricultural soils.

The tremendous losses of soil nitrogen resulting from the rapidnitrification of ammonium nitrogen, and the leaching and bacterialdecomposition of nitrate nitrogen have depleted many agricultural soilsof the nitrogen reserves and nitrogen requirements for plant nutrition.m order to replenish the soil nitrogen, the agriculturalist has resortedto the use of large amounts of nitrate fertilizers and reduced nitrogenfertilizers. In many instances, multiple fertilizer treatments duringthe growing season have been required to maintain adequate nitrogen soilor lost by denitrification, the application of nitrogen as reducednitrogen fertilizers provides the agricultural-',

ist with a short interval during which available reduced nitrogen is ata maximum and conditions for leaching and denitrification are at aminimum. This interval is particularly advantageous during the initialgrowth of seeds and emerging seedlings when high soil nitrogenconcentrations are very desirable. In addition, the am.-

monium nitrogen absorbed by plants is immediately available forassimilation into organic materials being synthesized thereby. Incontrast, the nitrate nitrogen must be reduced before it can beassimilated in the synthesis of plant materials. plant usually at theexpense of synthesized carbohydrate, Although some plants seem. to ,dowell on either ammonium nitrogen or nitrate nitrogen as a sourceoffnitro gen nutrients, many plants such as potato, corn, rice,buckwheat, pineapple, cotton and orange prefer ammonium nitrogen andappear to grow best in the presence of substantial amounts of this formof :"nitrogen. Thus, the need for a method of suppressing the'rapid lossof soil nitrogen is well recognized byagricult'uralis ts.

The latter This reduction is carried out in the,

, gen.

An object of the present invention is to provide a new andimprovedagronomic practice for conserving soil nitrogen. A furtherobject is the provision of a new and improved method for suppressing theloss of soil nitro- An additional object is the provision of a new andimproved method for suppressing the loss of ammonium nitrogen from soil.Another object is the. provision of a new and improved method forsupplying soil with nitrogen available for plant growth. Anotherobjectis the provision of a new and improved method for suppressing theloss of reduced nitrogen fertilizer supplements fromsoil. 'An additionalobject is the provision of a new and improved method for suppressing thenitrification of ammonium nitrogen in soil. Another object is theprovision of a new and improved method for suppressing the conversion insoil of ammonium ions to nitrate ions. An additional object is theprovision of novel compositions to be employed in the new methods of thepresent invention. Other objects will become apparent from the followingspecification and claims.

The new agronomical practice for improving plant nutrition andconserving soil nitrogen comprises treating plant growth media with ahaloalkane having a chain length of from 2 to 3 carbon atoms, inclusive,and having from 5 to 8 halogen atoms, inclusive, on the chain. Preferredhaloalkanes are those in which the halogen atoms are bromine orchlorine. The haloalkanes are liquids or solids adapted to be readilyand conveniently distributed in soil.

By the practice of this invention, the nitrification of ammoniumnitrogen in the soil to nitrate nitrogen is suppressed therebypreventing the rapid loss of amrrioniumnitrogen from the soil.Furthermore, by proper distribution of the haloalkane, this action ofinhibiting the transformation of ammonium nitrogen to nitrate nitrogenis effective over a prolonged period of time. The ammonium nitrogen mayarise from added ammonium nitrogen fertilizers or be formed in the soilby conversion of the organic nitrogen constituents found in soil oradded thereto as components of organic fertilizers.

The provision of an effective dosage of the haloalkanes in the soil orgrowth medium is essential for the practice of the present invention. Ingeneral, good results are obtained when the growth medium is modifiedwith the haloalkane in the amount of from 2 to 150 parts or more byweight of the latter per million parts by weight of growth medium. Infield applications, the compounds may be distributed in the soil in theamount of at least 0.5 pound per acre and through such a cross-sectionof the soil as to provide for the presence therein of aneffective'concentration of the agent. Itis usually preferred that thehaloalkane compound be distributed to a depth of at least two inchesbelow the soil surface and at a dosage of at least 0.7 pound per acreinch of soil. by dispersing very large dosages in growth media, aprolonged inhibition of nitrification may be obtained over a period ofmany months. The concentration of the active haloalkane compound iseventually reduced to a minimum by decomposition in the soil.

In one embodiment of the present invention, the haloalkane compound isdistributed throughout the growth media prior to seeding ortransplanting the desired crop plant.

:In another embodiment, the soil in the root zone of growing plants is.treated with the haloalkane compound in an amount effective to inhibitnitrification but sublethal to plant growth. In such'operations, thecompoundsshould be supplied in the soil in an amount no greater thanabout 50 parts by weight per million parts by weight of the soil. .Byfollowing such practice, no adverse effectlis exerted by the haloalkaneupon growth of seeds or plants, Oftentimes it is desirable to treat thesoil adjacent to plants, and this procedure may be carried outconveniently insiderdressing operations.

In a further embodiment; soil may-be treated with the 4 haloalkanefollowing harvest or after fallowing to pre vent rapid loss of ammoniumnitrogen and to build up the ammonium nitrogen formed by conversion oforganic nitrogen compounds. Such practice conserves the soil nitrogenfor the following growing season.

In an additional embodiment, the soil is treated with the haloalkane inconjunction with the application of reduced nitrogen fertilizers. Thetreatment with the haloalkane may be carried out prior to, subsequent toor simultaneously with the application of fertilizers. Such practiceprevents the rapid loss of the ammonium nitrogen added as fertilizer andthe ammonium nitrogen formed from the organic reduced nitrogen infertilizers by the action of soil bacteria. The administration to thesoil of the haloalkane as a constituent of an ammonium nitrogenfertilizer composition constitutes a preferred embodiment of the presentinvention.

The present invention may be carried out by distributing the haloalkanein an unmodified form through growth medium. The present method alsoembraces distributing the compound as a constituent in liquid or finelydivided solid compositions. In such practice, the haloalkane may bemodified with one or more additaments or soil treating adjuvantsincluding water, petroleum distillates or other liquid carriers,surface-active dispersing agents, finely divided inert solids andnitrogen fertilizers. De-

pending upon the concentration of the haloalkane, such augmentedcompositions may be distributed in the soil without further modificationor be considered concern trates and subsequently diluted with additionalinert carrier to produce the ultimate treating compositions. Therequired amount of the haloalkane may be supplied to growth media infrom I to 50 gallons of organic solvent carrier, in from 5 to 27,000 ormore gallons of aqueous carrier, or in from about 20 to 2,000 pounds ofsolid volume of aqueous liquid carrier.

The concentration of the haloalkane in compositions to be employed forthe treatment of growth media is not critical and may vary considerablyprovided the required dosage of effective agent is supplied to thegrowth media. The concentration of the haloalkane may vary from 0.00lpercent by weight to percent by weight of the composi-' tion, dependingon whether the composition is a treating composition or a concentratecomposition and whether it is in the form of a solid or a liquid. Inaqueous liquid treating compositions, concentrations of from 0.001percent to 0.25 percent by weight ofthe haloalkane is considered thepreferred composition. The concentration of the haloalkane in organicsolvents may be from 2.0 to 50 percent by weight. Concentrate liquidcompositions generally contain from 2.5 to 50 percent by weight of thehaloalkane compound. Solid compositions may contain the haloalkanecompound in amounts as high as 95 percent by weight of the haloalkanecompound. Treating compositions generally contain 0.004 percent'to 10percent by weight of the haloalkane. Concentrate compositions containfrom 2.5 to 95 percent of the haloalkane.

Liquid compositions containing the desired amount of the haloalkane maybe prepared by dispersing the latter in one or more liquid carriers suchas water oran organic solvent, with or without the aid of a suitablesurfaceactive dispersing agent or emulsifying agent. Suitable organicsolvents include acetone, diisobutylke tone, methanol, ethanol,isopropyl alcohol, diethyl ether, toluene. methylene chloride,chlorobenzene' and the petroleum distillates. The preferred organicsolvents are those which are of such volatility thatthey leave littlepermaabout 80 F. Dispersing and emulsifying agents which may be employedin liquid compositions include condensation products of alkylene oxideswith phenols and organic acids, alkyl aryl sulfonates, polyoxyalkylenederivatives of sorbitan esters, complex ether alcohols, mahogany soapsand the like. The surface-active agents are generally employed in theamount of from 1 to 20 percent by weight of the haloalkane.

Solid compositions containing the active haloalkane may be prepared bydispersing the latter in finely divided inert solid carriers such astalc, chalk, gypsum, vermiculite, bentonite and the like, fullers"earth, attapulgite and other clays, various solid detergent dispersingagents and the solid fertilizer compositions. In preparing suchcompositions, the carrier is mechanically ground with the haloalkane orwet with a solution thereof in a volatile organic solvent. Dependingupon the proportions of ingredients, these compositions may be employedwithout further modifications or be considered concentrates andsubsequently further diluted with solid surface-active dispersing agent,talc, chalk, gypsum or the like to obtain the desired treatingcomposition. Furthermore, such concentrate compositions may be dispersedin water with or without added dispersing agent or agents to prepareaqueous soil treating compositions.

Soil treatment compositions may be prepared by dispersing the haloalkanein fertilizers such as ammonium fertilizer or organic nitrogenfertilizer. The resulting fertilizer compositions may be employed assuch or may be modified as by dilution with additional nitrogenfertilizer or with inert solid carrier to obtain a compositioncontaining the desired amount of haloalkane for treatment of soil.'Further, an aqueous dispersion of the haloalkane fertilizer compositionmay be prepared and administered to the growth medium. Fertilizercompositions comprising the haloalkane in intimate admixture withammonium fertilizers constitute preferred embodiments of the presentinvention.

In fertilizer compositions comprising reduced nitrogen fertilizer, it isdesirable that the haloalkane be present in an amount of at least 0.5percent by weight based on the weight of the nitrogen present in thefertilizer as reduced nitrogen. Thus, when a fertilizer compositioncontains both reduced nitrogen and other forms of nitrogen such as inthe case of ammonium nitrate fertilizer compositions, the amount ofhaloalkane compound is based on the weight of nitrogen "present in'theammonium component.

In operations carried outin accordance with the present invention, thesoil may be impregnated in any convenient fashion with .the' haloalkaneor a composition containing the latter. compositions may be mechanicallymixed with the soil; applied to the surface of soil and thereafterdragged or disced into the soil to a desired depth; or transported intothe soil with a liquid carrier such as by injection, spraying orirrigation. When the distribution is carried out by introducing thehaloalkane in the water employed to irrigate the soil, the amount ofwater is varied in accordance with the moisture content of the soil inorder to obtain a distribution of the haloalkane compound to the desireddepth. The haloalkane may be readily and conveniently distributed to adepth of from two to four feet by irrigation methods. The preferredmethods embrace procedures using any of these steps or combination ofsteps wherein the compounds are distributed in the soil substantiallysimultaneously with a reduced nitrogen fertilizer.

The following examples illustrate the invention but are not to beconstrued as limiting.

EXAMPLE 1 An aqueous ammonium fertilizer composition containing 500parts by weight of nitrogen and 50 parts by weight of octachloropropaneper million parts of aqueous mediawas prepared by dispersing a 4 percent(weight For example, these modified or unmodified by volume of solvent)acetone solution of octachloropropane in aqueous ammonium sulfatesolution. (The amount of nitrogen in all examples is based on thenitrogen present in the fertilizer in the reduced form.)

The composition so prepared was employed to treat seed beds of sandyloam soil having a pH of about 8, containing essentially no organicmaterial, and having been freed of nitrite and nitrate nitrogen by priorthorough leaching with water. In the treating operation, the compositionwas applied to the seed beds as a soil drench, and the soil in the bedsthoroughly mixed to insure a substantially uniform distribution of thecomposition throughout the soil. Theamount of composition employed wassufiicient to supply parts by weight of nitrogen and 10 parts by weightof octachloropropane per million parts by weight of soil. In a checkoperation, other seed beds similarly prepared were fertilized with asimilar aqueous fertilizer composition containing the same amount ofacetone and ammonium sulfate but no octachloropropane. The compositionwas applied in an amount sufiicient to supply the same concentration ofnitrogen to the soil as the treating composition containingoctachloropropane. The soil temperature of all seed beds was maintainedat about 70 F. for the period of the determination.

At various intervals following treatment, samples of soil were takenfrom the different seed beds and the extent of nitrification of theadded ammonium sulfate fertilizer determined by analyses for combinednitrate plus nitritenitrogen. The determinations were carried out byextracting the nitrate and nitrite from the soil with a saturatedcalcium sulfate solution, developing color in the clear supernatant ofthe extract with diphenylamine in sulfuric acid, and comparing the colorwith a standard solution containing known concentrations of nitrate andnitrite ions. This procedure is similar to that described inColorimetric Methods of Analysis by F. D. Snell and C. T. Snell, D. VanNostrand Company, Inc., volume H, 3rd edition, page 801.

The percent nitrification in the seed beds of the added ammonium sulfateat various intervals is set forth in the following table:

Table 1 Percent Nitrification Interval Following Treatment in Days SoilTreated Soil Treated with Ammowith Ammonium' Sulfate nium SulfateQctaehloro- (Check) propane EXAMPLE 2 Ammonium sulfate and an acetonesolution containing 2 percent (weight by volume of solvent) of varioushaloalkanes were dispersed in water to prepare aqueous compositionscontaining 500 parts by weight of nitrogen and 25 parts by weight of ahaloalkane per million parts by weight of ultimate mixture. Thesecompositions were employed to treat sandy loam soil as described inExample 1 but employing amounts sufiicient to provide 100' parts byweight of nitrogen and 5 parts by weight of the Table II IntervalPercent Treating Composition Following Nitrifi- Treatment cation in DaysAmmonium sulfate 1,1,1,2,3,3 hexachloropronoun 7 O Ammonium sulfatecheck) 7 100 Ammonium sulfate 1,l,1,2,3,3-hexachloro pro ne 14 25Ammonium sulfate (cheek) 14 100 Ammonium sulfate 1,1,l,2 2 3 3heptachloropropane 7 5 Ammonium sulfate (check) 7 100 Ammonium sulfate1,1,1,2,2,3,3 heptachloropropane 14 10 Ammonium sulfate (check) 14 100Ammonium sulfate ootachloropropane 14 15 Ammonium sulfate (eheck)- 14100 EXAMPLE 3 Aqueous ammonium nitrate fertilizer composition containing1,000 parts by weight of nitrogen and 50 parts by weight ofl,l,1,2,2,3,3-heptachloropropane in a million parts of aqueous media wasprepared by dispersing an acetone solution containing 4 percent (weightby "volume of solvent) of 1,l,1,2,2,3,3-heptachloropropane in aqueoussolution of ammonium nitrate.

In an operation similar to that described in Example 1, the soil in seedbeds was treated with the above described composition to distribute thecomposition throughout the soil in an amount sufficient to supply aconcentration of nitrogen in the soil of 200 parts by weight and of1,1,1,2,2,3,3-heptachloropropane of 10 parts by weight per million partsby weight of soil. The treated soil was maintained at 70 F. and atvarious intervals, samples of the soil were taken and analyses made todetermine the extent of nitrification.

The soil Was analyzed for residual ammonia by extracting the soil with 2molar potassium chloride and the ammonia in the extract determined bycomparisons with a standard on a spot plate using Nesslers reagentasindicator. A determination carried out on the th day showed 0 percentnitrification. A determination on soil of a check operation carried outemploying a similar aqueous ammonium nitrate fertilizer compositioncontaining no 1,1,1,2,2,3,3 heptachloropropane showed 100 percentnitrification on the 20th day.

EXAMPLE 4 Aqueous ammonium fertilizer compositions containing 1,000pants by weight of nitrogen and parts by weight of1,1,1,2,2,3,3-heptabromopropane in a million parts of aqueous media areprepared by dispersing an acetone solution containing4 percent (weightby volume of solvent) of 1,1,1,2,2,3,3-heptabromopropane in aqueoussolutions of the following ammonium compounds: ammonium nitrate,ammonium sulfate, aqua ammonia, diammonium phosphate and monoammoniumphosphate.

In operations similar to that described in Example 1,

the soil in seed'beds is treated with the above described plus nitritenitrogen as previously described. The soils treated with ammoniumnitrate are analyzed for residual ammonia by extracting the soil with 2molar potassium chloride and the ammonia in the extract determined bycomparisons with a standard on a spot plate using Nesslers reagent asindicator. V I

Check operations are simultaneously carried out on other seed bedsemploying similar aqueous fertilizer composition but containing no1,1,l,2,2,3,3-heptabromopropane.

Determinations made at periodic intervals for three weeks show that soiltreated with fertilizer compositions move alllnitrate and nitritenitrogen constituents. A sufweight of soil.

containing 1,1,1,2,2,3,3-heptabromopropane undergoes no substantialnitrification while soil treated with fertilizer compositions containingno 1,1,l,2,2,3,3-heptabromopropane undergoes complete nitrification.

EXAMPLE 5 A solid fertilizer composition Was prepared as follows: (1) aninhibitor component was prepared by (a) mixing .and grinding together0.2 gram ,of 1,1,1,2,3,3-hexachloropropane and 0.3 gram of attapulgite,(b) adding 1.5 grams of pyrophyllite thereto and grinding the resultingmixture until a finely powdered uniform composition was obtained; (2) afertilizer component Was prepared by hammer-milling together a 50:50mixture by weight of ammonium sulfate and pyrophyllite to obtaina fineuniform composition; (3) the inhibitor component and fertilizercomponent were mixed together in various ratios on a roller mill toobtain soil treating compositions containing1,1,l,2,3,3-hexachloropropane in varying concentrations expressed inpercent based on the nitrogen in the composition. These compositionswere employed to fertilize various beds of sandy loam soil containingessentially no organic material and having a pH of about 8. The soilemployed had been previously leached to reficient amount of water wasadded to the various beds to give the soil in the beds varying moisturecontent. The beds were fertilized in areas to be planted by providingdepressions and adding thereto the fertilizer treating cornposition andthen covering the composition with soil. The

amount of compositions employed was sufiicient to sup' ply 160 parts byweight of nitrogen per million parts by The soil was maintained inthetemperature range of from 70 to 85 F. for three weeks. At the end ofthis period, samples of soil were analyzed for content of nitrate plusnitrite nitrogen to determine the extent of nitrification of the addedammonium sulfate. The results were compared with determinations made ona check operation wherein a fertilizer composition containing no1,1,l,2,3,3-hexachloropropane was employed. The results obtained aregiven in Table III.

Table III Concentration of 1,1,1,2,3,3-Hexa- Percent Incubation Percentchloropropane as Percent Based Moisture Period in Nitrificaon theNitrogen in the Oompoin Soil Days tion sition 20 21 8 20 21 20 21 12 0(check) 20 21 75 EXAMPLE 6 Irrigation water is modified by adding anacetone solu tion containing 5 percent (weight by volume of solvent) ofhexabromoethane to give a concentration 'of the halo alkane therein of50 parts by weight in a million parts of water. I

The water modified as described above is employed to irrigate dry sandyloam soilhaving a pH of 8 and previously leached to remove any nitriteand nitrate present. The depth of the sandy loam, bed is 20-21 inches.An amount of modified water-equal to 6 acre inches per acre of soil isadded and allowed to equilibrate in the soil by standing for severaldays. At the end ofthis period, samples of soilfrom various depths aretaken. To each sample a sufficient volume of an aqueous ammonium sulfatesolution containing 2,500: parts of nitrogen by weight per million partsof water is added to give a composition containing 100 parts by weightof nitrogen per million parts of soil. The fertilized soil samples arethereafter maintained in the temperature range of from 70 to 85 F. Atperiodic intervals, samples of the soil are taken and analyses made onthe nitrate plus nitrite nitrogen to determine the extent ofnitrification.

Analyses on samples of soil at various levels on the 7th and 20th daysafter the start of incubation show commercial control of nitrificationat levels to 10 inches depth.

A check operation is carried out by irrigating soil with unmodifiedwater. In determinations made on various layers of soil of the checkoperation, it is found that on the 7th and 20th days there is 100percent nitrification at all depths in the soil.

EXAMPLE 7 An aqueous soil treating composition containing 100 parts byweight of l,l,1,2,2,3,3-heptachloropropane, 1,000 parts by weight ofnitrogen as ammonium sulfate and 500 parts by weight of phosphorus asphosphoric acid was prepared by dispersing a 4 percent (weight pervolume of solvent) acetone solution of 1,1,1,2,2,3,3-heptachloropropaneinto an aqueous solution of ammonium sulfate and phosphoric acid.

Pots were prepared for planting with 500 grams of sandy loam soil havinga pH of 8 and a 4 percent moisture content. 200 milliliters of thetreating composition prepared as described above was poured over thesoil in the pots (an amount equal to about 1 inch of liquid) to supplyto the soil 1,1,1,2,2,3,3-heptachloropropane in an amount suflicient togive a concentration of 40 parts by weight per million parts by weightof soil and a concentration of nitrogen of 400 parts per million. Thetreated soil was then covered with paper to reduce evaporation andmaintained in the temperature range of from 70 to 80 F.

After a period of six weeks, the soil in the pots was leached with 6inches of water and thereafter each pot was planted with four tomatoplants. After an appropriate growth interval, the tops of the plantswere harvested just above ground level and weighed. The average freshweight in grams per pot was determined at the time of harvest which was35 days. I

A check operation was carried out simultaneously wherein soil in potswas similarly fertilized with a composition containing the same amountof ammonium sulfate, phosphoric acid and acetone but no 1,1,1,2,2,3,3-heptachloropropane. V

The weights of the plant tops at harvest in both the treating and checkoperations are set forth in Table IV.

Grams per Pot Ammonium sulfate phosphoric acid 1,1,1,2,2,3,3-

heptachloropropane acetone 11. Ammonium sulfate phosphoric acid acetone(check) 6.4

EXAMPLE 8 A solid fertilizer treating composition was prepared by (l)grinding together 1.0 part by weight of 1,1,1,2,2,3,3-heptachloropropane with 1.5 parts by weight of attapulgite, (2)mixing this mixture with 3 times its weight of pyrophyllite, and (3)mixing the resulting mixture with 9 times its weight of a 50/40 mixtureof ammonium sulfate and pyrophyllite. This treating compositioncontained 1 percent by weight of 1,l,1,2,2,3,3-heptachloropropane and 50percent by weight of ammonium sulfate.

Pots were prepared for planting with 500 grams of sandy loam soil havinga pH of 8 and a 4 percent mois ture content. 200 milliliters of aphosphoric acid solution containing 500 parts by weight of phosphorusper million parts of media was poured over the soil in the pots. Thesoil was then allowed to dry. Thereafter, a hole about %-1 inch deep wasmade in the center of each pot, and 2 grams of the solid fertilizertreating composition prepared as described above placed therein. Theholes were closed by compressing the soil together. The soil thustreated contained 40 parts by weight of 1,1,1,2,2,3,3-heptachloropropane and 400 parts by weight of nitrogen permillion parts by weight of soil. The pots were then covered with paperto reduce evaporation and maintained in the temperature range of from 70to F. for five weeks. At the end of this period, analyses were made onthe soil in certain of these pots for ammonium nitrogen. The soil in theother pots was leached with 6 inches of water and then planted with 4tomato plants per pot. After a growing period of 48 days, the tops ofthe plants were. harvested by cutting them off at the ground level andthe average fresh weight in grams per pot determined.

A check operation was carried 'out simultaneously.

Table V Y Weight of Treating Composition Fresh Tomato Plant Tops inGrams per Pot Phosphoric acid ammonium sulfate 1,1,1,2,2,3,-3-

heptachloropronane...; Phosphoric acid ammonium sulfate (check) EXAMPLE9 Concentrate compositions are prepared as follows:

(A) 25 parts by Weight of penta'bromomethane, 65 parts of xylene and 10parts of an alkylated aryl polyether alcohol (Triton X-100) aremechanically mixed together to obtain an emulsifiable liquidcomposition.

(B) parts by weight of 1,l,1,3,3-pentabromopropane and 10 parts of analkyl aryl sulfonate (Acto 700) are mechanically mixed together toobtain a water-dispersible mixture.

These compositions may be dispersed in Water to produce aqueouscompositions having desirable wetting and penetrating properties. Theseaqueous compositions are then employed to treat soil in an amountsuflicieut to distribute the haloalkane compound therein in efiectiveconcentrations. The concentrates may also be dispersed in aqua ammoniato prepare fertilizer compositions.

EXAMPLE 10 'Fertilizer compositions are prepared as follows:

(A) Hexachloroethane is mechanically mixed with ammonium phosphate toprepare a reduced nitrogen fertilizer composition containing 5 percentby weight of hexachloroethane.

(B) 1-bromo-1,l,2,2-tetrachloropropane is mechanically mixed withammonium nitrate to prepare a reduced nitrogen fertilizer compositioncontaining 3 percent by weight of l-bromo-l,1,2,2-tetrachloropropane.

These fertilizer compositions are distributed in soil to supply thenitrogen requirements for plant nutrition. The treated soil is resistantto nitrification and provides nitrogen available for plant growth over aprolonged period of time.

I claim:

1. A method for suppressing the nitrification of ammonium nitrogenpresent in soil and preventing rapid loss of ammonium nitrogen therefromwhich comprises 1 l impregnating soil below the soil' surfacein thegrowing area thereof in concentration sutficient to suppressnitrification, with a' haloalkane, said haloalkane having a chain lengthof from 2 to 3 carbon atoms, inclusive, and

having from 5 to 8 halogen atoms, inclusive, on the chain, s-aid halogenbeing selected from the'group consisting of bromine and chlorine, andsaid concentration being from about 2 to 150 parts by weight per millionparts by weight of soil; 7

2. A method according toclaim 1 wherein the haloalkane isoctachloropropane.

3. A method according to claim 1 wherein the haloalkane is1,l,1*,2,3,3-hexachloropropane.

4. A method according to claim 1 wherein the haloalka-ne is1,1,l,2,2,3,3-heptachloropropane.

5. A method according to claim 1 wherein the haloalkane ishexachloroethane.

6. A method according to claim 1 wherein the halonitrogen and to preventrapid loss of ammonium nitrogentrom soil which comprises impregnatingthe soil below the soil surface in the growing area thereof in an amountsufiieient to inhibit nitrification with a composition comprising ahaloalkane in intimate admixture with a soil treating adjuvant, thehaloalkane having a chain length of from 2 to 3 carbon atoms, inclusive,and having from 5 to 8 halogen atoms, inclusive, on the chain, saidhalogen being selected from the group consisting of, bromine'andchlorine and the impregnation being so 5 vant is a reduced nitrogenfertilizer composition wherein said reduced nitrogen fertilizer is afertilizer selected from the group'consisting of ammonia, ammonium saltsand urea. I

11. A fertilizer composition comprising a major 0' amount of a reducednitrogenfertilizer as source of ammonium ions and a haloalkane having achain length of from 2 to 3 carbon atoms, inclusive, and having from V 5to 8 halogen atoms, inclusive, on the chain, said halogen being selectedfrom the group consisting of bromine '5" and chlorine, and wherein thehaloalkane is present in a concentration of at least 0.5 percent byweight based on the weight of reduced nitrogen present in thefertilizer, andwherein said reduced nitrogen fertilizer is selected fromthe group consisting of ammonia, ammonium 20' salts and urea.

12. A fertilizer composition comprising a major amount of a reducednitrogen fertilizer as'source of ammonium ions and1,1,1,2,2,3,3-heptachloropropane as a haloalkane, and wherein saidhaloalkane is present in a 25 concentration of at least 0.5 percent byweight based on the weight of reduced nitrogen present in the fertilizerand said reduced nitrogen fertilizer is a fertilizer selected from thegroup consisting of ammonia, ammonium salts and urea.

Great Britain July 16, 1947

